Coupling

ABSTRACT

The invention provides for a trailer coupling which includes one or more torque elements having pads of elastic material interposed between an inner angular member and an outer angular member. The pads of the elastic material permit but resist relative vertical movement between the inner and the outer members. The inner and outer members are connected by linkages to attachment plates. The coupling can be attached to and between a draughting vehicle and a trailer to transmit traction force to the trailer. The resilient deformation of the pads of elastic material dampen relative vertical movement between the draughting vehicle and the trailer.

This application is a continuing application of application Ser. No.794,446 which was filed Nov. 4, 1985 and which issued as U.S. Pat. No.4,641,852 on Feb. 10, 1987.

This invention relates to a coupling. The invention relates moreparticularly to a trailer coupling for transmitting traction force froma draughting vehicle to a trailer.

According to the invention, there is provided a trailer couplingcomprising at least one torque element which is resililently yieldableunder torque, which is arranged to permit relative vertical movementbetween a draughting vehicle and a trailer, and which is further adaptedto resist such relative movement to thereby damp the relative movement.The trailer coupling further comprises two attachment plates, one forattaching the coupling to the draughting vehicle and the other forattaching the coupling to a trailer. The attachment plates are spacedapart from each other with the torque element between them and thetorque element is fast with one of the attachment plates and isoperatively associated with the other attachment plate by means of alinkage.

According to the invention, there is also provided a trailer couplingcomprising four torque elements, at least one torque element beingresiliently yieldable under torque, arranged to permit relative verticalmovement between a draughting vehicle and a trailer, and adapted toresist such relative movement to thereby damp the relative movement. Thetrailer coupling also comprises two attachment plates. One pair oftorque elements is fast with one of the attachment plates and the otherpair of torque elements is fast with the other attachment plate. Thetrailer coupling further comprises a set of linkages for interconnectingthe torque elements.

According to the invention, there is further provided a trailer couplingcomprising a plurality of torque elements having outer members. At leastone torque element is resiliently yieldable under torque, arranged topermit relative vertical movement between a drafting vehicle and atrailer, and adapted to resist such relative movement to thereby dampthe relative movement. The trailer coupling also comprises two spacedattachment plates, one for attaching the coupling to the draughtingvehicle and the other for attaching the coupling to the trailer. Eachattachment plate is integral in one piece from the same sheet materialwith the outer members of a pair of torque elements.

The torque element may include an outer tubular member of angularcross-section and an inner elongate member of angular cross-sectionwithin the tubular member, and a plurality of bodies of resilientmaterial interposed between the inner and the outer members to mount theinner member with clearance within the outer member. The bodies ofresilient material may be resiliently deformable to permit arcuatemovement of the inner member within the outer member but to resist suchmovement.

The outer member may be a tube of metal such as steel having a squarecross-section. The inner member may be a tube or a solid bar having asquare cross-section. the bodies of resilient material may be pads ofnatural or synthetic rubber which may be positioned in the corners ofthe outer member to locate the inner member securely but yieldablywithin the outer member.

In one arrangement the attachment plates may be separate plates securedto the outer tubular members of the torque elements, for example bywelding.

Alternatively, the attachment plates may be integral in one piece withone or more of the outer tubular members of the torque elements. In thisarrangement two outer tubular members may be formed from one piece ofsheet material with the two tubular members spaced apart from each otherby a section of the sheet material forming the attachment plate.

If desired, the coupling may include two torque elements, one being fastwith one of the attachment plates and the other being fast with theother attachment plate, and the elements being interconnected by meansof linkages.

The torque element may in an alternative arrangement include a torquespring. In another arrangement it may include a torsion bar.

The torque element may be so arranged within the coupling that in the atrest position there is a predetermined spacing between the twoattachment plates, and when the torque element is operated under atraction force, the distance between the attachment plates increases.

The invention is now described with reference to the accompanyingdrawings, in which:

FIG. 1 shows a three-dimensional view of one embodiment of a trailercoupling in accordance with the invention;

FIG. 2 shows a sectional view on line II--II of FIG. 1;

FIG. 3 shows a side view of the coupling shown in FIG. 1 mounted on adraughting vehicle;

FIG. 4 shows a three-dimensional view of another embodiment of a trailercoupling in accordance with the invention; and

FIG. 5 shows a sectional view on line V--V of FIG. 4.

Referring to FIGS. 1 to 3 of the drawings, reference numeral 10indicates one embodiment of the trailer coupling in general. It includestwo attachment plates 12 and 14 having holes 16 and 18 through whichfastening bolts may be passed for mounting the coupling.

The coupling 10 further includes four torsion elements 20 and 22 fastwith the attachment plate 12, and 24 and 26 fast with the attachmentplate 14. The torsion elements 20 and 24 are interconnected by means oflinkages 30, which the torsion elements 22 and 26 are interconnected bymeans of linkages 32.

Referring to FIG. 2, there is shown a cross-sectional view of thetorsion elements 24. The other torsion elements 20, 22 and 26 areidentical. The torsion element 24 includes an outer steel tube 34 ofsquare cross-section and a smaller bar 36 also of square cross-sectionwhich may be a tube as shown, or may be solid. The inner tube 36 isfitted within the outer tube 34 by means of four pads 38 of resilientmaterial such a natural or synthetic rubber fitted in the corners of theouter tube 34 so that the inner tube 36 is held in position within theouter tube 34. When the inner tube 36 is turned within the outer tube34, the resilient pads 38 are compressed, whereby torque is generatedwhich resists arcuate movement which tends to urge the inner tube 36 toan at rest position within the outer tube 34 as shown in FIG. 2. Theinner tube 36 is fast with the respective linkages 30 and 32 so that anymovement of the inner tube 36 within the outer tube 34 is transmittedthrough the respective linkage 30, 32, and vice versa.

Referring to FIG. 3, the trailer coupling 10 is shown mounted on therear end 40 of a draughting vehicle shown in dotted lines. The vehiclehas a bumper 42 and a drawbar 44 to which the attachment plate 12 of thecoupling 10 is secured by means of bolts 46. A trailer hook 48 shown indotted lines is secured to the attachment plate 14 of the coupling 10 bymeans of securing bolts 50. A trailer (not shown) may be attached to thetrailer hook 48.

In use, when the draughting vehicle 40 is in motion it transmitstraction force via the coupling 10 to the trailer hook 48, whereby thetrailer (not shown) is drawn. The traction force tends to increase thedistance between the attachment plates 12 and 14, but this is resistedby the torque elments 20, 22, 24 and 26 in a manner described withreference to FIG. 2. When the traction force is constant the distancebetween the attachment plates 12 and 14 will remain fairly constant, butif the traction force should vary such as could happen when thedraughting vehicle accelerates or decelerates, or if the trailer shoulddecelerate, for example by hitting some obstacle, the variation in thetraction force will be resisted by the torque elements 20, 22, 24 and 26in the coupling 10, and this will tend to dampen the relative movementbetween the draughting vehicle and the trailer.

Referring further to FIG. 3, the coupling 10 is shown in the unloadedcondition. When a trailer is attached to the trailer hook 48, it isloaded by the mass of the trailer's draw arm (not shown) actingvertically on the trailer hook 48. This load acting vertically on thehook causes the attachment plate 14 to move vertically down relative tothe plate 12. This causes the linkages 30, 32 to assume an appoximatelyhorizontal position against the bias of the torque elements 20,22,24,26.Relative vertical movements between the plates 12 and 14 are resisted byand thus dampened by the bias of the torque elements 20,22,24,26. Thisensures that the loading of the trailer hook 48 is maintained reasonablyconstant and thus that the loading on the driving wheels of the drawingvehicle 40 is also maintained reasonably constant. The dampening of therelative vertical movements further protects the draw bar 44 againstexcessive forces which could damage the draw bar or could wrench it fromthe draughting vehicle 40.

Referring to FIGS. 4 and 5, there is shown by reference numeral 60another embodiment of a trailer coupling in accordance with theinvention. Coupling 60 is similar to coupling 10 of FIGS. 1 to 3 but isof a lighter and more compact construction. It includes four torqueelements 62 similar to the torque elements 24 of FIGS. 1 to 3 with likenumbers indicating like items. The torque elements 62 are formed inpairs with each pair being formed in one piece from a single sheet ofmetal 64. Along the region 66, the sheet metal overlays itself and thisforms an attachment plate similar to the plates 12,14 in FIGS. 1 and 3.Holes 68, similar to holes 16 in FIG. 1, extend through the attachmentplates 66 for receiving fixing bolts (not shown) similar to the bolts46,50 shown in FIG. 3. Plugs 70 are provided for covering the ends ofthe inner tubes 36 of the torque elements 62.

The coupling 60 is attached in the same manner as the coupling 10described with reference to FIG. 3 and operates in the same manner.

We claim:
 1. A trailer coupling comprising at least one torque elementwhich is resiliently yieldable under torque, which is arranged to permitrelative vertical movement between a draughting vehicle and a trailer,and which is further adapted to resist such relative movement to therebydamp the relative movement, and two attachment plates, one for attachingthe coupling to the draughting vehicle and the other for attaching thecoupling to a trailer, the attachment plates being spaced apart fromeach other with the torque element positioned between them, the torqueelement being fast with one of the attachment plates and beingoperatively associated with the other attachment plate by means of alinkage.
 2. A trailer coupling as claimed in claim 1, in which thetorque element includes an outer tubular member of angular cross-sectionand an inner elongate member of angular cross-section within the tubularmember, and a plurality of bodies of resilient material interposedbetween the inner and the outer members to mount the inner member withclearance within the outer member.
 3. A trailer coupling as claimed inclaim 2, in which the bodies of resilient material are resilientlydeformable to permit arcuate movement of the inner member within theouter member but to resist such movement.
 4. A trailer coupling asclaimed in claim 2, in which the outer member is a tube having a squarecross-section, the inner member is a member having a squarecross-section, and the bodies of resilient material are pads of elasticmaterial positioned in the corners of the outer member to locate theinner member securely but yieldably within the outer member.
 5. Atrailer coupling as claimed in claim 1, in which in the at rest positionthere is a predetermined spacing between the two attachment plates, andwhen the torque element is operated under a traction force, the distancebetween the attachment plates increases.
 6. A trailer coupling asclaimed in claim 1, which is further arranged to permit relativemovement between the draughting vehicle and the trailer in the directionof the traction force and is adapted to resist such relative movement.7. A trailer coupling as claimed in claim 1 in which when the couplingis loaded by the trailer, the attachment plates move vertically relativeto one another.
 8. A trailer coupling comprising four torque elements,at least one torque element being resiliently yieldable under torque,arranged to permit relative vertical movement between a draughtingvehicle and a trailer, and adapted to resist such relative movementthereby damp the relative movement, two attachment plates, one pair oftorque elements being fast with one of the attachment plates and theother pair of torque elements being fast with the other attachment plateand a set of linkages for interconnecting the torque elements.
 9. Atrailer coupling comprising a plurality of torque elements having outermembers, at least one torque element being resiliently yieldable undertorque, arranged to permit relative vertical movement between adraughting vehicle and a trailer, and adapted to resist such relativemovement to thereby damp the relative movement, and two spacedattachment plates, one for attaching the coupling to the draughtingvehicle and the other for attaching the coupling to the trailer, eachattachment plate being integral in one piece from the same sheetmaterial with the outer members of a pair of torque elements.